Generally, as a rotary electric machine for a railway vehicle, a hermetic rotary electric machine is often employed from the viewpoint of saving on maintenance. The hermetic rotary electric machine is configured to mainly include a cylindrically-shaped frame in which a rotor is arranged on its inner peripheral side and housings that are provided at opposite ends of the frame and rotatably support a rotor shaft. A bearing is provided at a center portion of the housing, and a cylindrical stator iron core in which a stator coil is accommodated is mounted on an inner peripheral portion of the frame. A uniform gap is formed between an inner peripheral surface of the stator iron core and an outer peripheral surface of the rotor.
In the hermetic rotary electric machine configured as described above, periodic maintenance needs to be performed on the bearing although cleaning work for the rotor and the like is unnecessary. At the time of maintenance, it is a common procedure that the rotor is first pulled out from the frame, and then the bearing is removed.
As means for saving this work, a traction motor shown in Patent Literature 1 mentioned below has a mode in which a rotor is fixed by a plurality of bolts inserted from the bearing bracket side toward the rotor, and thereafter a housing having a bearing fixed thereon is detached.